The invention relates to an indexing device and method for reproducing the axis of a universal joint mounted dental impression holder.
In the making of partial bridges, the dentist reviews the patient's teeth impressions to determine the patient's best natural teeth to use for the surface attachment of the clips of a partial bridge. The method to determine the best natural teeth involves taking the patient's impression and securing it to a support table by mounting clamps. The mounting clamps are located on the support table which is attached to a support stand by a universal joint to allow the dentist freedom to move an impression secured by the mounting clamps to the support table relative to an index rod that is supported by the support stand. By angularly adjusting the support table with respect to the index rod, the teeth profiles with the greatest curvature are easily determined and can be marked. The impression is then sent to a dental laboratory where the dental bridge is made.
An alignment problem exists at the laboratory. While the attachment teeth are known by the markings, reproduction of the angularity of the support table at the laboratory to that used by the dentist can only be approximated.
The instant invention provides an indexing method and apparatus whereby the angularity of the support table of the dentist can be exactly reproduced at the laboratory.
The reproduction is made possible by the dentist drilling an alignment hole in the impression when the desired orientation of the impression and the index rod is obtained. The orientation of a drilling guide and the index rod are fixed and parallel to one another. Knowing this relationship and having a duplicate orientation mechanism at the laboratory allows the technician at the laboratory to insert a positioning rod into the drill holder of the laboratory support mechanism and the drilled hole in the impression to thus replicate the angle used by the dentist.
To accomplish the alignment method, a drill guide alignment arm is fixedly attached to the index rod, or the support arm for the index rod. The alignment arm is provided with a drill guide hole that extends parallel to the index rod. When the dentist finds the desired orientation of the impression with respect to the index arm, the support table is clamped to prohibit movement. A drill is then inserted into the drill guide and is used to drill an alignment hold into the impression.
When the impression reaches the laboratory, it is clamped onto the laboratory support table and oriented to a position where an alignment rod, that is inserted into the drill guide hole, can enter into the hole that the dentist previously drilled in the impression. At that point, the orientation of the technician's support table and that of the dentist is the same. Accordingly, the technician no longer has to worry about approximating the dentist's orientation.